Thermodynamic properties of 56,57Fe

Nuclear level densities for 56,57Fe have been extracted from the primary γ-ray spectra using (3He, 3He'γ) and (3He, αγ) reactions. Nuclear thermodynamic properties for 56Fe and 57Fe are investigated using the experimental level densities. These properties include entropy, Helmholtz free energy, caloric curves, chemical potential, and heat capacity. In particular, the breaking of Cooper pairs and single-quasiparticle entropy are discussed and shown to be important concepts for describing nuclear level density. Microscopic model calculations are performed for level densities of 56,57Fe. The experimental and calculated level densities are compared. The average number of broken Cooper pairs and the parity distribution are extracted as a function of excitation energy for 56,57Fe from the model calculations